Use of wireless communication devices has grown exponentially over the years. Devices such as computers and telephones that were once restricted by wires now benefit from advances in wireless technologies. Enabling wireless communication is an antenna that transmits and/or receives electromagnetic waves. Because an antenna is the means by which the communication device transmits and/or receives a signal, the performance of the antenna is an important ingredient in any wireless communication.
Recently, the need for high data rate applications in compact communication devices has pushed the envelope of antenna technologies. To achieve high data rate, transmission frequencies have steadily increased, thereby decreasing the wavelength of the radio frequency band. For example, mobile devices operating in the millimeter wavelength range (30 to 300 GHz bandwidth) are capable of transferring data in the multi-gigabit-per-second range. One advantage of the smaller wavelength is that the size of the antenna may be decreased, thereby permitting communicating devices to become smaller and more compact. However, one disadvantage of the smaller wavelength is the higher propagation loss in the interconnections between the antenna and the transceiver, which directly affects communication performance. For example, increase in the interconnection length between the antenna and transceiver reduces the communication range of the wireless device. As such, an on-chip antenna (i.e. an antenna integrated on the same semiconductor substrate as the transceiver) is the optimal solution for communication devices operating in the millimeter wavelength range.
There have been attempts to develop on-chip antennas. However, because standard silicon substrate such as Complementary Metal Oxide Semiconductor (CMOS) and Silicon-Germanium (SiGe) are incompatible with antenna substrate requirements (i.e. low resistivity of CMOS and SiGe), on-chip antennas have often been inefficient and impractical for real world use. While techniques such as micro machining to remove the low resistivity substrate under the antenna and on-chip dielectric resonator antenna have been proposed to increase the efficiency of the on-chip antenna, fabrication complexity, cost and packaging issues have prevented such techniques from being used widely.
Off-chip antennas such as horn and lens antennas overcome the efficiency issues faced by on-chip antennas; however, they are expensive and are too bulky to be integrated into mobile communication devices.
Therefore, there is a need for a low-cost and highly efficient antenna that can be integrated into the transceiver.